Follow along with the countdown! The Virtual Launch Control Center is the only place online to get breaking information directly from NASA's Kennedy Space Center in Florida. Live countdown coverage will begin about six hours prior to launch and will conclude about 10 minutes after liftoff, when orbit insertion is complete. Coverage includes frequent updates on the countdown status and videos of key events.

The countdown clock is one of the most-watched timepieces in the world. On this page, you'll learn how the countdown operates, and what milestones to watch for during our Live Launch Coverage.

Image to left: Spectators gather on the grounds in front of the countdown clock during a space shuttle launch. Credit: NASA

Here are some of the key events that take place at each milestone after the countdown begins. Note: Event times and lengths are approximate and subject to change.

Image to right: The space shuttle launch team seated in Kennedy's Firing Room 1.
Credit: NASA

Image to right: The rotating service structure is rolled slowly into the "park" position, revealing Space Shuttle Atlantis as the launch countdown for STS-98 enters its final hours. Credit: NASA

Image to right: Space Shuttle Discovery waits to launch on mission STS-103. At the top is the external tank gaseous oxygen vent arm system with the vent hood (sometimes called the "beanie cap") poised above the external tank. Extending toward the cabin of the orbiter below is the orbiter access arm, with the White Room at the end. Credit: NASA

Image to right: A fish-eye view captures Space Shuttle Endeavour just after liftoff on mission STS-111. Credit: NASA

It was an exciting year in 2006 and 2007 for science on the International Space Station. New research facilities were installed and new investigations had begun, while the results of a wide variety of investigations began to be published in scientific literature. Here are just a few highlights of the past year, and some great investigations to watch for in the remainder of 2007.

MISSE

Results from previous investigations in the Materials on the International Space Station Experiment (MISSE), suite have enabled a major step forward in understanding atomic oxygen undercutting underneath protective coatings, as well as in the development of a comprehensive set of models and observations for existing and new spacecraft materials. These experiments also have successfully proved several types of more efficient advanced solar cells with an understanding of their efficiency and performance in the space environment.

Image at right: This image of the MISSE-3 Passive Experiment Container (PEC) was taken on December 18, 2006. At this point, MISSE-3 has been exposed to the space environment for approximately 4 months. Credit: NASA

MISSE 3 and 4, which are the latest in a series of suitcase-sized testbeds attached to the outside of the space station, were successfully deployed during extravehicular activity, or EVA 5, on August 3, 2006. Approximately 875 specimens of various materials contained in suitcase-like cases called passive experiment containers were mounted directly to the outside of the station and will remain there for approximately one year until the 13A.1 (STS-118) flight. The samples are for 40 different investigators including NASA centers, military space organizations and aerospace contractors and manufacturers. These specimens will be exposed to the harsh environment of microgravity to observe the effects that atomic oxygen, ultraviolet light and thermal conditions have on materials.

The specimens include a variety of materials such as paint and protective coatings that will be used on future spacecraft such as satellites. Environmental monitors will record the thermal cycling, or change in temperature, that is occurring. New material that might be used in the next generation of EVA suits is being tested to examine how that material reacts to the harsh environment.

Three million basil seeds have been placed in containers that are located underneath the trays on MISSE 3 and 4. Once the seeds have been returned to Earth, they will be distributed to school children for them to plant and observe the differences between seeds exposed to space and seeds that have remained on Earth.

MELFI and Nutrition Status Assessment

Getting the Minus Eighty Degrees Celsius Laboratory Freezer for ISS (MELFI) operating on orbit and starting comprehensive medical studies that rely on it was another significant accomplishment of 2006. MELFI provides the space station with refrigerated volume for storage and fast-freezing of life science and biological samples. It also ensures transportation of conditioned specimens to and from the station by flying in fully powered mode inside the Multi-Purpose Logistics Module, or MPLM. Before MELFI, it was not possible to assess nutritional status during flight because blood and urine could not be collected, stowed frozen and returned during space station missions.

Image at right: Expedition 14 Commander and NASA Astronaut Michael Lopez-Alegria inserts blood and urine samples into the Minus Eighty Degree Laboratory Freezer for ISS (MELFI) until they can be returned to Earth for analysis. Credit: NASA

One of the first investigations to take advantage of sample storage in MELFI is Nutrition Status Assessment (Nutrition). This experiment is about a lot more than nutrition -- it goes to the heart of human physiology in space. Data from typical medical monitoring on the station indicated significant declines in vitamin D status related to bone loss, folate, and vitamin B-6; significant loss of body mass; and unhealthy increases in serum iron. As a medical experiment, Nutrition will give us the first profiles of changes in important physiological indicators during the course of a long-duration mission. Beginning with the Expedition 14 crew, blood and urine samples are being collected near Flight Days 15, 30, 60, 120, and 180 and then stored in the MELFI freezer for future return.

The experiment significantly expands the number of biomarkers to be measured in the blood and urine. Additional markers of bone metabolism will be measured to better monitor bone health and countermeasure efficacy. New markers of oxidative damage will be measured to better assess the type of radiation and other oxidative impacts during space flight. The array of nutritional assessment parameters will be expanded to better understand changes in folate, vitamin B-6 status and related cardiovascular risk factors during and after flight. Additionally, stress hormones and hormones that affect bone and muscle metabolism will be measured. This investigation represents the most comprehensive monitoring of a broad array of physiological indicators that NASA has ever completed for long-duration space flight.

SPHERES

In 2006 and 2007, the crew performed one-, two-, and three-unit tests of formation flying for Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES). These are iterative tests with dynamic computer learning inside the station cabin in which bowling ball-sized spheres perform various maneuvers with the spheres operating simultaneously. The investigators have moved through several substantial changes in software, and the spheres have learned how to negotiate the cabin environment and maintain positions relative to one another.

Image at right: Three satellites fly in formation as part of the Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) investigation. This image was taken during Expedition 14 in the Destiny laboratory module. Credit: NASA

Information learned from this experiment may lead to simpler autonomous docking allowing for servicing, re-supplying, reconfiguring and upgrading of space systems. SPHERES results also support the development of autonomous spacecraft to carry out a variety of tasks in a space environment. Smaller autonomous spacecraft could, with the right coordination and programming, perform tasks too complicated or too expensive for larger spacecraft to execute.

New Opportunities for Students to Participate in Space Experiments

The University of Colorado in Boulder and BioServe Space Technologies have launched the first of a planned series of investigations that will allow students to participate in space research. The Commercial Generic Bioprocessing Apparatus Science Insert – 01 (CSI-01) was delivered to the station on the 12A.1 (STS-116) flight in December 2006. It included two different types of habitat inserts—for seed germination and for culturing roundworms called Caenorhabditis elegans, or C. elegans.

Image at right: This image shows several Caenorhabditis elegans, small nematode worms, on-orbit during Expedition 14 on January 24, 2007. Credit: NASA

The worm experiment began on January 10, 2007 on the station. It builds on previous biological studies of worms in space as model organisms for studying risks associated with radiation, microgravity and other variables experienced in the space environment. Partnered with the Orion’s Quest curriculum, the C. elegans experiment involves over 5,000 middle school students in the United States and several thousand students in Malaysia. The C. elegans were returned to Earth during the 13A (STS-117) mission in June 2007.

The seed germination experiment began February 16, 2007, with more than 2,000 third graders participating in this pilot program. The curriculum for the student investigations is being implemented in partnership with Agronauts at North Carolina State University in Raleigh. The students grow radish and alfalfa seeds in their classrooms at the same time as the seeds germinate and grow on orbit. Students then examine root and stem growth of the two plants and compare seeds germinated on Earth to those germinated on the space station. The results of these experiments will help students understand the concept of gravitropism as well as issues scientists face when planning to grow plants in space.

Top Science Activities to Watch for in 2007:

Integrated Immune

A new study of the immune system in orbit will start with the 10A (STS120) flight. We know that crew members show all kinds of signs of degradation in immune function during long-duration flight; a few times it has already put missions at risk of early termination. There are several possible causes ranging from microgravity to stress to radiation. To devise a countermeasure to prevent immune dysfunction, a valid monitoring technique must be developed. The Integrated Immune study will obtain comprehensive measurements of the different immune pathways during the mission so that we will know which compartments of the immune system are really affected, allowing the development of targeted countermeasures. Since there are no procedures currently in place to monitor immune function or its influence on crew health, we are looking forward to the results of this experiment.

SAME

The Smoke and Aerosol Measurement Experiment (SAME) will be delivered to the station on the 10A (STS-120) flight. This experiment burns sample space materials, measures the soot and smoke particles and compares the two different technologies used in shuttle and the station smoke detectors to identify their performance in detecting smoke from a variety of sources. Since shuttle experimental data shows that smoke, like flames, is much different in microgravity, this experiment will determine the best smoke-detection technology. Results from this experiment will help identify ways to improve smoke detectors on future spacecraft. Crew Exploration Vehicle teams are also waiting for the data to finalize their smoke detection requirements. In addition to analyzing smoke detection, SAME will impact fire-suppression approaches.

EPO-Kit C

The Education Payload Operations - Kit C Plant Growth Chambers (EPO-Kit C) is part of the 13A.1 (STS-118) mission. This experiment is an on-orbit plant growth investigation using basil seeds. The still and video imagery acquired will be used as part of a national engineering design challenge for students in grades K-12. Students will grow basil seeds -- control and flown seeds -- to conduct their own science experiments on plant growth using growth chambers created by the students on the ground.

Image at right: Basil plants grown from seeds, on Earth, in a simple plant growth chamber (opened). Credit: NASA

On orbit, crew members will capture video of the transfer of two, small collapsible growth chambers for EPO-Kit C. The video will include a discussion of the growth chambers by the crew members and will be used during Phase I and Phase II of the national engineering design challenge. The video will be distributed to education organizations to be incorporated into education products for students in grades K-12. Crew members also will conduct a 12-day to 21-day on-orbit plant growth investigation using basil seeds. The plant growth inside the growth chambers will be documented with still digital imagery.

Multigen

Molecular and Plant Physiological Analyses of the Microgravity Effects on Multigeneration Studies of Arabidopsis thaliana (Multigen) is a cooperative investigation with the European Space Agency (ESA). This experiment will examine the growth of Arabidopsis thaliana (thale cress) over three generations to determine the effects of microgravity on the plant. Multigen will utilize the European Modular Cultivation System (EMCS) facility on board the International Space Station. EMCS is an experiment facility for biological investigations in microgravity.

The investigation will have three phases. In the first phase (Multigen-1), the seeds will grow and develop into mature seed-bearing plants after watering on the station. These plants will be dehydrated to harvest the seeds. The seeds will be stowed and returned to Earth for morphological testing. A portion of the seeds will be returned to the station for the second generation of thale cress plants for Multigen-2. Once the second generation of plants reaches maturity and bears seeds, the plants will be dehydrated once again and the seeds will be harvested. These seeds will be stowed on the station and returned to Earth for morphological studies. A portion of these seeds will be returned to the station for Multigen-3. Once the third generation of plants reaches maturity, the plants will be dehydrated and stowed for return to Earth for further testing.